Intake bypass flow management systems and methods

ABSTRACT

Filtration systems having a normal filtration mode and an enhanced filtration mode are described. In some arrangements, the filtration system is an air filtration system having a primary air filter element, a pre-cleaner, and a pre-cleaner bypass valve. Based on feedback from an intake air quality sensor the bypass valve is either opened or closed to selectively route intake air through the pre-cleaner during sensed dirty air operating conditions (e.g., heavy dust or moisture concentrations). In other arrangements, the filtration system is a liquid filtration system (e.g., a fuel or oil a secondary filter. The filtration system selectively routes the liquid being filtered through the main filter, the secondary filter, or a combination thereof depending on a detected event or sensed characteristic of the liquid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/027,984, entitled “AIR INTAKE BYPASS FLOW MANAGEMENT SYSTEMS ANDMETHODS,” filed on Jul. 23, 2014, which is herein incorporated byreference in its entirety and for all purposes.

TECHNICAL FIELD

The present disclosure relates generally to filtration systems.

BACKGROUND

Internal combustion engines typically include various filtrationsystems, such as air filtration systems, fuel filtration systems, oilfiltration systems, and the like. The filtration systems generallyremove contaminants, such as dust and water, from fluids used by theinternal combustion engine.

The air filtration system is part of an air intake system. The airfiltration system filters intake air prior to routing the intake air tothe engine. The air filtration systems remove dust, moisture, and otherparticulate from the intake air. The air filtration systems typicallyinclude a filter media (e.g., a paper-based filter media, a foam-basedfilter media, a cotton-based filter media, a pleated filter media, etc.)that processes the air. Some air filtration systems include apre-cleaner positioned upstream of the filter media. A pre-cleanerremoves at least a portion of the dust, moisture, and other particulatematter from the intake air prior to the intake air being processed bythe filter media. Accordingly, the pre-cleaner extends the life of thefilter media. The pre-cleaner may be an ejective pre-cleaner, apre-filter pre-cleaner, a cyclonic pre-cleaner, or the like. Thespecific type of pre-cleaner may be selected based on the worst dustloading conditions that an internal combustion engine is expected to seeduring operation.

A pre-cleaner, however, also causes parasitic air pressure losses in theair intake system due to the increased restriction caused by thepre-cleaner. The parasitic losses are present even when the pre-cleaneris unnecessary (e.g., when the internal combustion engine is operatingin a clean air environment). The parasitic losses may cause higherpumping loss, thereby reducing the fuel economy for the internalcombustion engine (e.g., reduced miles per gallon in a vehicleapplication, fewer operating hours per tank in a generator orconstruction application, etc.). The reduced fuel economy increasesoperating costs (i.e., increases fuel costs).

Other filtration systems, such as fuel, oil, and hydraulic fluidfiltration systems, filter liquids that are used by the internalcombustion engine or used to drive equipment. Generally, thesefiltration systems draw fluid to be filtered from a tank (e.g., a fueltank, an oil tank, a hydraulic fluid tank, etc.). Certain operatingconditions can cause the fluid to have increased contamination levels.Specifically, contaminant particles may be re-entrained from thesurfaces of piping, filter media, tank bottoms, and the like duringcertain transient conditions, such as fluid flow surges, vibrations, andthe like. This is particularly problematic during tank fill up andengine or hydraulic system start up events. During tank fill ups,elevated contamination levels may be found in the new (but frequentlynot clean) liquid introduced into the tank. Contaminant levels arefurther increased by the resuspension of contaminant from tank bottomsand walls by the filling operation itself When an engine or hydraulicsystem is started, the liquid flow rate to the downstream components,including the filtration system, goes from zero to operating flow ratesin a matter of seconds or even less. As such, extremely highcontamination levels are temporarily observed as the fluid acceleratesfrom a generally stationary position to a moving stream. During theseperiods, wear induced damage to downstream components is especiallyhigh. Orders of magnitude increases in fuel contamination levels havebeen observed at engine start up and during rapid changes in flow rate.Such increases in the liquid born contamination reduce component life,reduce engine reliability, and reduce overall system robustness. Theseincreases in contamination levels also have the potential to shorten theuseful life of the filtration system. Additionally, the introduction ofthe multiple filter elements, much like the above-described pre-cleanersfor air filtration systems, introduces greater restriction to thefiltration systems thereby causing parasitic liquid pressure losses inthe filtration systems.

SUMMARY

One embodiment relates to an air filtration system. The air filtrationsystem includes a primary filter element and a pre-cleaner positionedupstream of the primary filter element in an air flow direction. The airfiltration system further includes a bypass valve actuatable between afirst position and a second position. When the bypass valve is in thefirst position, intake air to be filtered bypasses the pre-cleaner andflows to the primary filter element. When the bypass valve is in thesecond position, intake air to be filtered is forced through thepre-cleaner prior to flowing to the primary filter element. The airfiltration system further includes an air quality characteristic sensorand a controller. The controller is configured to receive a feedbacksignal from the air quality characteristic sensor indicative of a sensedair quality characteristic of the intake air and to actuate the bypassvalve between the first position and the second position via anactuation mechanism.

Another embodiment relates to a filtration system. The filtration systemincludes a fluid source providing a fluid to be filtered, a main filter,a secondary filter, and a detector that detects a fill-up condition, astart-up condition, a change in fluid contaminant concentration, or afluid flow rate change of a system using the fluid. The filtrationsystem further includes a valve that can be opened or closed to switchthe filtration system between a normal filtration mode and an enhancedfiltration mode. The enhanced filtration mode corresponding to anoperating mode in which an increased amount of the fluid to be filteredthrough the secondary filter element than when in the normal filtrationmode. The filtration system includes an electronic control unit having amemory and a processor. The electronic control unit is configured toreceive a feedback signal from the detector indicative of a fill-upevent, a start-up event, a change in fluid contaminant concentration, ora fluid flow rate change, and to switch between the normal filtrationmode and the enhanced filtration mode in response to the fill-up event,the start-up event, the change in fluid contaminant concentration, orthe fluid flow rate change.

A further embodiment relates to a method of switching a filtrationsystem between a normal filtration mode and an enhanced filtration modebased on a detected event. The method includes receiving, by anelectronic control unit of the filtration system, a feedback signal froma sensor of the filtration system. The method further includesdetermining, by the electronic control unit, that the feedback signalcorresponds to a fill-up event or a start-up event. The method includesactivating, by the electronic control unit, the enhanced filtration modeof the filtration system. The enhanced filtration mode corresponds to anoperating mode of the filtration system in which an increased amount ofthe fluid to be filtered passes through an filtration component thanwhen in the normal filtration mode.

Another embodiment relates to a filtration system. The filtration systemincludes a fluid source providing a fluid to be filtered, a main filter,and a secondary filter. The filtration system further includes a fluidquality characteristic sensor that senses a fluid quality characteristicof the fluid. The filtration system includes a valve that can be openedor closed so as to switch the filtration system between a normalfiltration mode and an enhanced filtration mode. The enhanced filtrationmode corresponds to an operating mode in which an increased amount ofthe fluid to be filtered is filtered through the secondary filterelement than when in the normal filtration mode. The filtration systemincludes an electronic control unit having a memory and a processor. Theelectronic control unit is configured to receive a feedback signal fromthe detector indicative of a change in the fluid quality characteristicof the fluid, and to switch between the normal filtration mode and theenhanced filtration mode in response to the change in the fluid qualitycharacteristic.

A further embodiment relates to a filtration system. The filtrationsystem includes a fluid source providing a fluid to be filtered, a mainfilter, and a secondary filter. The filtration system includes adetector that detects a fill-up condition, a start-up condition, achange in fluid contaminant concentration, or a fluid flow rate changeof a system using the fluid. The filtration system further includes apump that routes the fluid to the secondary filter such that the pumpcan be activated and deactivated to switch the filtration system betweena normal filtration mode and an enhanced filtration mode. The enhancedfiltration mode corresponds to an operating mode in which an increasedamount of the fluid to be filtered is filtered through the secondaryfilter than when in the normal filtration mode. The filtration systemincludes an electronic control unit having a memory and a processor. Theelectronic control unit is configured to receive a feedback signal fromthe detector indicative of a fill-up event, a start-up event, a changein fluid contaminant concentration, or a fluid flow rate change, and toswitch between the normal filtration mode and the enhanced filtrationmode in response to the fill-up event, the start-up event, the change influid contaminant concentration, or the fluid flow rate change byactivating the pump.

These and other features, together with the organization and manner ofoperation thereof, will become apparent from the following detaileddescription when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic view of an air filtration system according to anexemplary embodiment.

FIG. 2 is a close-up schematic view of each sensor of the air filtrationsystem of FIG. 1.

FIG. 3 is a close-up schematic view of the bypass valve of the airfiltration system of FIG. 1.

FIG. 4 is a close-up schematic view of a bypass valve according to anexemplary embodiment.

FIG. 5 is a block diagram of an electronic control unit according to anexample embodiment.

FIG. 6 is a flow diagram of a method of switching a filtration systembetween a normal filtration mode and an enhanced filtration mode basedon a detected event according to an example embodiment.

FIGS. 7 through 10 show, schematic views of liquid filtration systemsare shown according to example embodiments

DETAILED DESCRIPTION

Referring to generally to the figures, filtration systems having both anormal filtration mode and an enhanced filtration mode are shown. Thenormal filtration mode corresponds to an operating condition in whichfluid being filtered is routed through a primary filtration system andbypasses a secondary filtration system. The enhanced filtration modecorresponds to an operating condition in which fluid to be filtered isrouted through both the primary filter and the secondary filter. Theenhanced filtration mode is used when the fluid to be filtered containsa higher than normal level (i.e., an elevated level) of contaminants,such as water, dust, and the like or when there is a fluid flow rateincrease (e.g., when an operator increases the throttle of an internalcombustion engine). The normal filtration mode is used when the fluid tobe filtered contains a normal level or lower than normal level ofcontaminants or when fluid flow conditions are at a normal orsteady-state rate.

FIGS. 1-4 generally relate to an air filtration system. The airfiltration system filters intake air prior to routing the intake air toan internal combustion engine. The air filtration system includes aprimary filter element comprised of a filter media (e.g., a paper-basedfilter media, a foam-based filter media, a cotton-based filter media, apleated filter media, etc.). The air filtration system also includes apre-cleaner positioned upstream of the primary filter element. The airfiltration system is fitted with a control system that includes a sensor(e.g., a dust particle sensor, a moisture sensor, a turbidity sensor,etc.) and a flow bypass valve mechanism that, when opened, allows intakeair to bypass the pre-cleaner and flow directly to the primary filterelement. Based on feedback from the sensor (e.g., a feedback signalindicative of an air quality measurement, an amount of dust in the air,an amount of moisture in the air, etc.) the bypass valve is eitheropened or closed. During sensed clean air operating conditions (e.g.,low dust and moisture concentrations), the bypass valve is opened toallow intake air to bypass the pre-cleaner, thereby providing a lowresistance air flow and better fuel economy. During sensed dirty airoperating conditions (e.g., heavy dust or moisture concentrations), thebypass valve is closed thereby routing intake air into the pre-cleanerto increase the service life of the primary filter element. The overallair filtration system provides for an overall (i.e., average) betterfuel economy rating than those systems without the bypass valve.

FIGS. 5-9 generally relate to a liquid filtration system. The liquidfiltration system may be a fuel filtration system, an oil filtrationsystem, or a hydraulic fluid filtration system. The liquid filtrationsystems draw fluid to be filtered from a storage tank. The filtrationsystem detects tank fill-ups or engine or hydraulic system start-upevents through sensors (e.g., fluid flow sensors, fluid qualitycharacteristic sensors, etc.) or detectors (e.g., an ignition switch)that produce an electrical output or signal. A controller, such as theelectronic control module (ECU) of the engine or hydraulic system, thatmonitors and receives the output from the sensor or detector. When thecontroller receives a signal indicating a fill-up or start-up event, thecontroller can put the filtration system into an enhanced filtrationoperating mode for a period of time. In some arrangements, thecontroller puts the filtration system into the enhanced mode ofoperation when the flow of fluid through the filtration system iselevated above a normal fluid flow rate or is changing. While in theenhanced filtration operating mode, the filtration system routes fluidthrough additional filtering components than the normal filtrationoperating mode to remove potential elevated contamination levels fromthe fluid. The enhanced mode of operation continues for a time intervaldetermined by the controller. Alternatively, the enhanced mode ofoperation continues while a fluid flow rate is changing or elevatedabove a normal fluid flow rate. After the time interval expires or thefluid flow rate through the filtration system returns to a normal orstead-state flow rate, the filtration system is returned to its normalmode of operation.

Referring to FIG. 1, a schematic view of an air filtration system 100 isshown according to an exemplary embodiment. The air filtration system100 filters intake air 102 and routes the intake air 102 to a device,such as an internal combustion engine (e.g., of a vehicle, a generator,construction equipment, etc.). The air filtration system 100 includes aprimary filter element 104 housed within a filter housing 106. Theprimary filter element 104 may be a paper-based filter media, afoam-based filter media, a cotton-based filter media, a pleated filtermedia, a panel filter element, a cylindrical filter element, or anothertype of filter element. The primary filter element 104 removes at leasta portion of the dust, moisture, and other particulate matter from theintake air 102. The air filtration system 100 also includes apre-cleaner 108 positioned upstream of the primary filter element 104 inan air flow direction. The pre-cleaner 108 may be an ejectivepre-cleaner, a pre-filter pre-cleaner, a cyclonic pre-cleaner, or thelike. When intake air is routed through the pre-cleaner 108, thepre-cleaner 108 removes at least a portion of the dust, moisture, andother particulate matter from the intake air 102 prior to the intake airbeing processed by the primary filter element 104. When the intake air102 is routed through the pre-cleaner 108, the restriction of the airfiltration system 100 is higher than if the pre-cleaner 108 was notpresent.

The air filtration system 100 includes a bypass control system. Thebypass control system includes a bypass flow valve 110, a bypass intake112, a sensor 114, and a controller 202 (as shown in FIG. 2). Althoughshown as including two sensors 114, the air filtration system 100 may beconfigured to work with a single sensor 114 (e.g., a single sensor 114positioned upstream of a bypass valve, which is also positioned upstreamof both the pre-cleaner 110 and the bypass intake 112). The sensor 114measures an air quality characteristic of intake air 102. The airquality characteristic may relate to an amount of dust in the air, anamount of moisture in the air, or a combination thereof. The sensors 114may be any of a dust particle sensor, a moisture sensor, a turbiditysensor, a capacitance sensor, or the like. The sensors 114 providefeedback signals indicative of the sensed air quality characteristic toa controller 202 of the bypass control system. In some arrangements, thecontroller 202 is an engine control module (“ECM”) of an internalcombustion engine.

The controller 202 opens and closes the bypass flow valve 110 based onthe measured air quality characteristic (e.g., based on the feedbacksignal received from the sensors 114). When the sensor feedbackindicates that the intake air 102 is clean (e.g., contains a low levelof dust and moisture), the controller 202 actuates the bypass flow valve110 to a first, open position creating a first air flow path for the airfiltration system 100. The first air flow allows the intake air 102 tobypass the pre-cleaner 108 and flow to the primary filter element 104.When the sensor feedback indicates that the intake air 102 is dirty(e.g., contains greater than a threshold level of dust or moisture), thecontroller 202 actuates the bypass flow valve 110 to a second, closedposition creating a second air flow path for the air filtration system100. The second air flow path forces the intake air 102 to pass throughthe pre-cleaner 108 prior to flowing to the primary filter element 104.The second air flow path has a higher air restriction than the first airflow path. The second air flow path increases the life of the primaryfilter element 104 during dirty air conditions. It should be understoodthat the flow paths of the air filtration system 100 can be configuredin an opposite manner (e.g., such that the pre-cleaner 108 is bypassedby the intake air 102 when the bypass flow valve 110 is closed).

Referring to FIG. 2, a close-up schematic view of each sensor 114 isshown according to an exemplary embodiment. As the intake air 102 passesthrough or by the each sensor 114, each sensor 114 senses the airquality characteristic. In some arrangements, the air qualitycharacteristic is sensed by counting and sizing particles passing by orthrough each sensor 114. In other arrangements, the air qualitycharacteristic is sensed by measuring an opacity or transparency of theintake air 102 by passing a light or laser through the intake air 102.For example, the intake air 102 may pass between two parts of eachsensor 114: a light emitting part and a light sensing part. In theexemplary arrangement, the light emitting part emits light into thelight sensing part. The opacity of the intake air 102 is determinedbased on how much or how little light is sensed by the light sensingpart. The opacity of the intake air 102 corresponds to the amount ofdust and moisture in the intake air 102. In an alternative arrangement,the air quality characteristic is sensed by measuring a moisture contentof the intake air 102. In still further arrangements, the air qualitycharacteristic is sensed by measuring a capacitance or inductance of theintake air 102.

FIG. 3 shows a close-up schematic view of the bypass valve 110 ofFIG. 1. The bypass valve 110 includes a flap 302 and a hinge 304. Thehinge 304 is positioned near the bypass intake 112. The hinge 304permits the flap 302 to pivot about the hinge 304 between a firstposition and a second position. In the first position, the flap 302 ispivoted away from the bypass intake 112 placing the bypass valve 110 inthe open position thereby permitting the intake air 102 to travel alongthe first air flow path as discussed above. In the second position, theflap 302 is pivoted towards the bypass intake 112 placing the bypassvalve 110 in the closed position thereby forcing the intake air 102 totravel along the second air flow path as discussed above. A valveactuation mechanism 306 moves the flap 302 between the first positionand the second position. In some arrangements, the valve actuationmechanism 302 can maintain the flap 302 in any position between thefirst position and the second position thereby allowing at least aportion of the intake air 102 to flow through the pre-cleaner 108 and aportion of the intake air 102 to bypass the pre-cleaner 108. The valveactuation mechanism 302 is controlled by the controller 202 based on thefeedback signals from the sensors 114.

FIG. 4 shows a close-up schematic view of a bypass valve 400 accordingto an exemplary embodiment. The bypass valve 400 is similar to and analternative to the bypass valve 110. For ease of explanation, similarreference numbers and terms will be used to describe the alternativebypass valve 400. Unlike the bypass valve 110 opening and closing a flap302, bypass valve 400 functions by opening and closing a plurality oflouvers 402. Each of the louvers 402 includes a slat and a centralhinge. The louvers 402 move together between an opened position (wheneach slat is substantially perpendicular to axis 406) and a closedposition (when each slat is substantially parallel to axis 406). Whenthe louvers 402 are in the opened position, intake air 102 bypasses thepre-cleaner 108 (i.e., travels along the first air flow path asdiscussed above with respect to FIGS. 1-3). When the louvers 402 are inthe closed position, the intake air 102 is forced to pass through thepre-cleaner 108 (i.e., travels along the second air flow path asdiscussed above with respect to FIGS. 1-3). A valve actuation mechanism404 moves the louvers 402 between the opened position and the closedposition. The valve actuation mechanism 404 is controlled by thecontroller 202 based on the feedback signals from the sensors 114.

The above described pre-cleaner bypass systems and methods allow foradaptable air filtration systems having additional restriction inpre-cleaners for better dust separation when actually separating dust,without sacrificing restriction when handling clean air flow through theuse of a bypass valves. The systems and methods manage unnecessary lossof pressure while flowing through pre-cleaner or moisture removal systemis avoided.

As described below in further detail, similar concepts may be applied toother types of filtration systems, such as fuel, oil, and hydraulicfluid filtration systems. In certain filtration systems that filterfluid received from a tank (e.g., a fuel tank, an oil tank, a hydraulicfluid tank, etc.), certain operating conditions can cause the fluid tohave increased contamination levels. Specifically, contaminant particlesmay be re-entrained from the surfaces of piping, filter media, tankbottoms, and the like during fluid flow surges that can be caused bytank fill ups and engine or hydraulic system start up events.

Referring to FIG. 5, a block diagram of an ECU 500 is shown according toan example embodiment. The ECU 500 controls the operation of afiltration system. Specifically, the ECU 500 toggles the filtrationsystem between a normal filtration mode and an enhanced filtration mode.In the enhanced filtration operating mode, fluid to be filtered passesthrough additional filtration components than the normal filtrationmode. The ECU 500 generally includes a processor 502, memory 504, and aninput/output (I/O) 506. The memory 504 includes programming modulesthat, when executed by the processor 502, control the operation of theECU 500, and thus control the operation of the filtration system.

Through the I/O 506, the ECU 500 monitors feedback signals to determinewhen a fill-up and/or start-up event is detected. Fill-up and/orstart-up events can be detected by the ECU 500 by sensing whether afluid tank's fill cap is in place or has been removed, by sensingchanges in a liquid level in the fluid tank, by sensing whether theinternal combustion engine or hydraulic system fed by the filtrationsystem has been turned on (e.g., by determining a key on situation), bysensing whether liquid flow has been initiated through the filtrationsystem, and/or by measuring changes in the flow rate through thefiltration system. Accordingly, the ECU 500 can communicate with varioussensors (e.g., fluid tank cap sensors, tank fluid sensors, flow ratesensors, engine control modules, hydraulic system control modules,engine ignition sensors, fluid quality characteristic sensors, etc.).Example fluid sensing techniques and systems are described in U.S.Publication No. 2010/0327884, U.S. Publication No. 2011/0140877, andU.S. Pat. No. 4,173,893, each of which are incorporated herein byreference in their entireties and for all purposes. In somearrangements, it is desirable to convert an analog output of any of theabove-described sensors to a digital output to facilitate sensor outputto the ECU 500. In such arrangements, the digital nature of the sensorfeedback signals allows the ECU 500 to be programmed to interpret thefeedback signals to distinguish insignificant changes in liquid level orflow rate from noteworthy events, such as filling operations orstart-ups (e.g., as described in further detail below).

Through the I/O 506, the ECU 500 can actuate valves and diverters of thefiltration system to switch between the normal filtration mode and theenhanced filtration mode. The ECU 500 switches between the operatingmodes based on the feedback received from the above-described sensors.Additionally, through the I/O 506, the ECU 500 can communicate with anoperator or technician through a user indicator (e.g., a display, anLED, a dashboard indicator, etc.).

In some arrangements, the ECU 500 can distinguish between fill-upevents, fluid flow rate changes, and start-up events, as the highestcontaminant levels in the fluids stored in the tanks are expected tooccur during filling operations due to re-suspension of settledcontaminant (such as from the tank bottom) and the introduction of newcontaminant from the new fluid. Accordingly, the ECU 500 can put thefiltration system into the enhanced filtration mode for a longer periodof time for a fill-up event and a shorter period of time for a system orengine start-up event. To distinguish between the two, the ECU 500 mayrely on a combination of sensing technologies (e.g., fluid tank capsensors, fluid characteristic sensors, and fluid flow-rate sensors).Alternatively, the ECU 500 can receive input from a location sensor(e.g., a GPS transponder) to compare a location of the vehicle orequipment with locations of known service stations or filling terminals.If either the engine is turned on or the flow rate increases from zeroto a working flow rate while near (e.g., within 20 meters) the locationof a service station, the ECU 500 can interpret the event as a fillingevent. If the vehicle is not near a service station, the ECU 500interprets the event as a simple start-up event.

The operation of the ECU 500 in specific systems is described in furtherdetail below with respect to FIGS. 6 through 10.

Referring to FIG. 6, a flow diagram of a method 600 of switching afiltration system between a normal filtration mode and an enhancedfiltration mode based on a detected event is described according to anexample embodiment. Method 600 is performed by a filtration systemcontroller, such as ECU 500. In method 600, the filtration system isnormally operated in the normal filtration mode. The filtration systemcan be temporarily switched into an enhanced filtration mode based ondetected events (e.g., a fill-up event or a start-up event).

The method 600 begins when a fill-up event occurs at 602 or a start-upevent occurs at 604. A fill-up event relates to a situation in which atank storing liquid to be filtered by the filtration system is filledwith additional liquid. A start-up event occurs when an internalcombustion engine or hydraulic system using the liquid filtered by thefiltration system starts-up. The fill-up event or start-up event may bedetermined by the above-described sensors or detectors. For example, afill-up event can be determined by sensing whether the liquid tank'sfill cap is in place or has been removed or by sensing changes in theliquid level in the tank. A start-up event can be determined by sensingor detecting whether the engine or hydraulic system has been turned onor by sensing whether liquid flow through the filtration system has beeninitiated or is experiencing a change in the flow rate.

Feedback signals from the sensors are received at the ECU 500 at 606.Based on the feedback signals from the sensors, the ECU 500 candetermine the existence of the fill-up event (that occurs at 602) or thestart-up event (that occurs at 604). The ECU 500 determines whether afill-up event occurred based on the sensor feedback signals at 608. If asignal indicating a fill-up event is indicated, the ECU 500 determines aduration of enhanced filtration mode at 610. The duration of enhancedfiltration mode represents the time period for which the filtrationsystem is in the enhanced filtration mode before reverting back to thenormal filtration mode. In some arrangements, the duration represents anamount of time needed to filter an amount of fluid filtered during theenhanced filtration mode. In a further arrangement, the durationrepresents an amount of time needed to remove an amount of contaminantfrom the fluid or to return the fluid to a threshold contamination levelas sensed by a sensor. Still further, the duration may represent anamount of time needed for the flow rate of the fluid to stabilize or toreturn to a normal flow as measured by a flow meter or a flow ratesensor. The duration of the enhanced filtration mode is a relativelyshort term enhanced filtration response used to reduce contaminationlevels in the fluid. If a fill-up event was not detected at 608, the ECU500 proceeds to determine whether a start-up event occurred at 614.

If a signal indicating a start-up event is indicated, the ECU 500determines a duration of enhanced filtration mode at 610. The durationof enhanced filtration mode represents the time period for which thefiltration system is in the enhanced filtration mode before revertingback to the normal filtration mode. In some arrangements, the durationrepresents an amount of time needed to filter an amount of fluidfiltered during the enhanced filtration mode. In a further arrangement,the duration represents an amount of time needed to remove an amount ofcontaminant from the fluid or to return the fluid to a thresholdcontamination level as sensed by a sensor. Still further, the durationmay represent an amount of time needed for the flow rate of the fluidthrough the filtration system to stabilize or to return to a normal flowas measured by a flow meter or a flow rate sensor. In some arrangements,the durations of enhanced filtration mode for a fill-up event and for astart-up event are different. For example, the duration of enhancedfiltration mode may be longer for a fill-up event than for a start-upevent. The duration of the enhanced filtration mode is a relativelyshort term enhanced filtration response used to reduce contaminationlevels in the fluid.

In either case, if a fill-up event is detected at 608 or if a start-upevent is detected at 614, the enhanced filtration mode is activated at612 for the amount of time determined at 610. As described in furtherdetail below with respect to FIGS. 7-10, the enhanced filtration modecan be achieved in different manners. For example, the ECU 500 canactuate a valve that increases the flow rate of the fluid through akidney loop portion of the filtration system (e.g., as shown in FIG. 7).As an additional example, the ECU 500 can activate a diverter thatdiverts the fluid flow through an additional prefilter upstream of themain filtration system (e.g., as shown in FIG. 8). As an additionalexample, the ECU 500 can initiate a duplex or multiplex mode offiltration (e.g., as shown in FIG. 9). As a further example, the ECU 500can open and close valves to stop fluid flow through the main filtrationsystem and increase flow through a kidney loop filtration system (e.g.,as shown in FIG. 10). In some arrangements, a combination of the aboveenhanced filtration mode techniques is implemented by the ECU 500 for adefined duration to reduce contamination levels in the fluid toacceptable levels.

If no fill-up event is detected at 608 and no start-up event is detectedat 614, the filtration system is set to the normal filtration mode at616. Likewise, if a fill-up event is detected at 608 or if a start-upevent is detected at 614, the filtration system is set to the normalfiltration mode at 616 after the determined duration (determined at 610)expires during 612. The ECU 500 continues to monitor the sensor feedbacksignals during operation after the filtration system is placed in thenormal filtration mode at 616.

Referring to FIGS. 7 through 10, schematic views of liquid filtrationsystems are shown according to example embodiments. Each of thedescribed filtration systems includes the ECU 500, a liquid tank 702, afill-up and/or start-up detector 704, a main filter 706, and an engineor hydraulic system 708. In some arrangements, the main filter 706includes a plurality of filters. In each of FIGS. 7 through 10, thicklines indicate plumbing connecting the tank 702 to the variouscomponents of the filtration systems, such as the main filter 706 andthe engine or hydraulic system 708. Plumbing from the engine orhydraulic system 708 back to the tank 702 is indicated as dashed lines,which represents that this section of plumbing exists only inarrangements where the fluid is recirculated. For example, lubricationand hydraulic fluid is typically recirculated, while fuel is generallyburned by an internal combustion engine. Although some fuel filtrationsystems route a portion of the filtered fuel back to the tank 702. Stillreferring generally to FIGS. 7 through 10, thin lines connect the ECU500 with the detector 704 and other components (e.g., an actuated valveor a pump). The thin lines represent operational electronic (e.g., hardwire or wireless) connections between these components.

The fluid tank 702 is fitted with one or more detectors 704, such as anyof the above-described detectors. The detectors 704 may be located inany appropriate location. In the figures, one detector 704 is shown inthe bottom of the tank for illustrative purposes only. It should beunderstood that detectors may be placed outside of the tank 702 (e.g.,at the tank filling cap, at the engine or hydraulic system 708, alongany of the fluid lines, etc.). Each of the detectors 704 is operativelyconnected to the ECU 500 as indicated by the black arrow. When the ECU500 receives a feedback signal or output indicative of a fill-up event,a start-up event, a fluid flow change, a fluid quality characteristic,or the like, the ECU 500 can send a signal to an actuated valve or pumpto activate an enhanced filtration mode (e.g., as described above withrespect to method 600) by opening or closing a valve or by controllingpump speed. Typically, the ECU 500 controls the duration of the enhancedfiltration mode. The duration may be based on an amount of time (e.g.,as calculated by a timer of the ECU 500, a change in flow rate of thefluid (e.g., as determined based on a fluid flow sensor feedbacksignal), a quality of characteristic of the fluid (e.g., as determinedby a fluid quality characteristic sensor), or a combination thereof. Thecharacteristics of the filters are not described in this invention,although it is understood that the main filter 706 is designed to reducecontamination to acceptable levels with acceptable service life andrestriction for the application, and other filters are intended toprovide performance characteristics adequate to temporarily reduce theexcessively high contaminant concentrations found after fill-up andstart-up events.

Referring specifically to FIG. 7, a schematic view of a filtrationsystem 700 is shown. The filtration system 700 effectuates the enhancedfiltration mode by increasing the flow rate of the fluid through akidney loop filter 710. The kidney loop filter 710 is part of a fluidrecirculating loop (i.e., a kidney loop portion) of the filtrationsystem 700. During normal operation of the filtration system, fluidflows continuously through the both the kidney loop and main filtrationlines when the engine or hydraulic system 708 is running In somearrangements, however, it may be desirable for there to be no flow inthe kidney loop portion during normal operation. At start-up andimmediately upon filling the tank 702, the flow rate through the kidneyloop portion, including the kidney loop filter 710, is increased torapidly decrease contaminant levels in the fluid. The magnitude andduration of the increased flow rate through the kidney loop filter 710is governed by application considerations, including but not limited tothe volume of the tank 702, contamination sensitivity of the downstreamcomponents, and the residence time of fluid in the tank 702 during theenhanced filtration mode of operation.

To switch between the enhanced filtration mode and the normal filtrationmode, the ECU 500 controls an actuated valve 712. The actuated valve 712may be located upstream or downstream of the kidney loop filter 710.When the ECU 500 receives a signal or output indicative of a fill-up orstart-up event from the detector 704, the ECU 500 sends a signal to anactuated valve 712 that is operatively connected to the ECU 500. Thesignal causes the actuated valve 712 to open (or to open further)thereby reducing the restriction in the kidney loop portion of thefiltration system 700 and enabling increased flow to pass through thekidney loop filter 710. The location where the kidney loop portionbranches off from the main filtration line may occur at any appropriatepoint, but is preferably upstream of main filter 706. In somearrangements, a pump 714 is used to further induce fluid flow throughthe kidney loop portion. In such arrangements, it may not be necessaryto use the actuated valve 712 because the ECU 500 can directly controlflow rate through the kidney loop portion via the pump 714.

Referring to FIG. 8, a schematic view of a filtration system 800 isshown. The filtration system 800 effectuates the enhanced filtrationmode by diverting the fluid flow through an additional prefilter 802upstream of the main filter 706. During normal filtration modeoperation, the actuated valve 804 is open thereby allowing fluid tocontinuously flow only through the main filter 706 when the engine orhydraulic system 708 is running (i.e., the fluid bypasses the prefilter802 during normal filtration mode operation). At start-up andimmediately upon filling the tank (i.e., during enhanced filtration),the ECU 500 closes the actuated valve 804 thereby forcing fluid flowthrough the prefilter 802 prior to passage through the main filter 706.By passing the fluid through the prefilter 802 prior to passing thefluid through the main filter 706, the contaminant concentration in thefluid going to the main filter 706 is reduced, which increases the mainfilter 706 life and the life of downstream components. In an alternativearrangement, a second filter is placed downstream of the main filter 706instead of having a prefilter placed upstream of the main filter 706. Insuch an arrangement, the second filter is used only during start-up andfill-up events in a similar manner as described above with respect tothe prefilter 802. Similar to the filtration system 700, a pump 806 maybe used to increase fluid flow rate through the prefilter 802 and/orthrough the main filter 706.

Referring to FIG. 9, a schematic view of a filtration system 900 isshown. The filtration system 900 effectuates the enhanced filtrationmode by initiating duplex or multiplex filtration. During normalfiltration mode operation, an actuated valve 902 remains closed, whichforces the fluid to flow only through the main filter 706 when theengine or hydraulic system 708 is running At start-up and immediatelyupon filling the tank (i.e., during enhanced filtration), the ECU 500opens the actuated valve 902 thereby allowing fluid flow through boththe main filter 706 and at least one auxiliary filter 904. In somearrangements, an additional actuated valve is positioned in fluidcommunication with the main filter 706 branch. In such arrangements, itis possible to completely divert flow through the auxiliary filter 904such that no fluid flows through the main filter 706. Although only oneauxiliary filter 904 is shown in FIG. 9, it should be understood that aplurality of auxiliary filters may be employed. By diverting at least aportion of the fluid flow through the auxiliary filter 904, the flowrate through the main filter 706 is reduced, which also reduces loadingto the main filter 706 and increases the life of the main filter 706.Additionally, by diverting at least a portion of the fluid flow throughthe auxiliary filter 904, the overall contaminant concentrations in thefluid may be reduced to any downstream components. The filtration system900 permits an alternating filter approach in which the fluid flowduring normal operation could be directed through either the main filter706 or the auxiliary filter 904. That is one of the main filter 706 andthe auxiliary filter 904 could be used as the “main filter” for a firstperiod of time, and the other of the main filter 706 and the auxiliaryfilter 904 could be used as the “main filter” for a second period oftime. This alternating filter approach enables balanced loading of themain filter 706 and the auxiliary filter 904, which advantageouslyallows the two filters to be serviced at the same time rather thanreplacing one filter sooner than the other filter. Similar to thefiltration systems 700 and 800, a pump 906 may be used to increase fluidflow rate through the main filter 706 and the auxiliary filter 904.

Referring to FIG. 10, a filtration system 1000 is shown. The filtrationsystem 1000 is similar to the filtration system 700. Accordingly, likenumbering is used with respect to the filtration systems 1000 and 700.The sole difference between the filtration system 1000 and thefiltration system 700 is the position of the actuated valve 712, whichis described in further detail below. Similar to the filtration system700, the filtration system 1000 effectuates the enhanced filtration modeby routing fluid through a kidney loop portion of the filtration system1000 that includes the kidney loop filter 710. During normal operationof the filtration system 1000, the actuated valve 712 is open permittingfluid flow through the main filter 706 and to the engine or hydraulicsystem 708. Following fill-up or start-up events detected by the ECU 500based on feedback from the detector 704, the ECU 500 sends an output tothe actuated valve 712 to fully or partially close the actuated valve712, which temporarily increases the fluid flow through the kidney loopfilter 710. Thus, the main filter 706 and any downstream components donot see total contamination load per unit time despite the elevatedcontaminant concentrations, and the main filter 706 and downstreamcomponents are protected from any spikes in contaminant concentration ofthe liquid thereby increasing their lives, increasing equipmentreliability, and increasing system robustness.

As discussed above, the filtration system 1000 can enter the enhancedfiltration mode with the actuated valve 712 fully closed or partiallyopen. In arrangements where the actuated valve 712 is fully closed,fluid flow through the main filter 706, and thus to the engine orhydraulic system 708, is cut off. Accordingly, this option is onlypractical if actual operation of the equipment using the engine orhydraulic system 708 can be delayed until the fluid is cleaned. In otherarrangements, the actuated valve 712 remains partially open followingfill-up or start-up events to enable a small amount of the fluid to passthrough to the main filter 706 and on to the engine or hydraulic system708 to enable minimal operation of the engine or hydraulic system 708(e.g., engine idling) to occur during the time that the fluid is beingcleaned by the kidney loop filter 710.

Regardless of the particular filtration system used, the enhancedfiltration mode is implemented by the ECU 500 immediately afterdetection of a fill-up event, a start-up event, another transient event(e.g., events that cause changes in fluid flow rate through thefiltration system), and upon start-up or initiation of fluid flow fromthe tank 702. The enhanced filtration mode is continued temporarilyuntil one or more of the following conditions occurs (1) until apredetermined time has elapsed, (2) until a predetermined volume offluid has been filtered, (3) until contamination levels in the fluidhave dropped to acceptable levels as determined by an actual or virtualcontamination sensor, (4) until the flow rate of fluid through hefiltration system has stabilized for a defined period of time, or (5)when the flow rate of fluid through the filtration system has returnedto a normal flow rate. Once one or more of the above-noted conditions isachieved, the ECU 500 sends an appropriate output signal to return thesystem to its normal or typical operating mode or condition. Inarrangements where the enhanced filtration mode stops after apredetermined time has elapsed, the predetermined time may be calculatedas a function of the residence time of the fluid during operation in theenhanced filtration mode. Normally, the predetermined time should be atleast three times the residence time. In arrangements where the enhancedfiltration mode stops after a predetermined volume of fluid has beenfiltered, the predetermined volume is typically a function of the tank702 volume. Normally, the predetermined volume to be filtered during theenhanced filtration mode should be at least three times the tank volume.In arrangements where the enhanced filtration mode stops aftercontamination levels of the fluid have been reduced to an acceptablelevel, a contamination sensor, such as a portable particle counter orother type of contamination sensor, can be fluidly connected to thesystem (e.g., immediately downstream of the tank 702) and electronicallyconnected to the ECU 500 to provide an output signal indicative of thecontaminant concentration. When the contamination reaches an acceptablelevel of cleanliness, such as an ISO 4406 code of 18/16/13 in fuel asmeasured using a portable particle sensor, the ECU 500 then outputs asignal to discontinue enhanced filtration mode.

As previously mentioned, in some arrangements it is desirable todistinguish between fill-up and start-up events, as contamination levelsare likely to be higher after fill-up events. In response to determiningdifferent events, different enhanced filtration modes can be implementedby the ECU 500 depending on the type of event. For example, one (ormore) of the enhanced filtering modes can be used in response tostart-up events for a first time period or volume of fluid filtered, andthe same enhanced filtering modes can be used in response to fill-upevents for a longer period of time or a greater volume of fluidfiltered. For example, if a period of time of three minutes is used forstart-up events, a period of time of six minutes or longer can be usedfor fill-up events. The above-described enhanced filtration modes canalso be applied in response to other detected events, such as eventsthat cause fluid flow surges (e.g., as occur when depressing theaccelerator). For example, the enhanced filtration mode can be used inresponse to rapidly changing fluid flow rates and continue for a periodof time (e.g., three minutes) after the flow rate stabilizes. In sucharrangements, the enhanced filtering mode may be implemented for adifferent time period or volume of fluid filtered than for fill-up orstart-up events.

The above-described filtration systems 700, 800, 900, and 1000 aredescribed with respect to providing fluid to an engine or hydraulicsystem 708. However, it should be appreciated that the enhancedfiltration modes described in the filtration systems 700, 800, 900, and1000 can also be applied to bulk storage tanks for fluid or otherapplications not directly attached to an engine or hydraulic system. Forexample, by removing eliminating the engine or hydraulic system 708 inany of the in any of the filtration systems 700, 800, 900, or 1000, theresultant system can be used with bulk storage or dispensing tanks inwhich the fluid from the main filter 706 is recirculated and/ordispensed.

As utilized herein, the terms “approximately,” “about,” “substantially,”and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numerical ranges provided. Accordingly, these terms shouldbe interpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the invention as recited in theappended claims.

It should be noted that the term “exemplary” or “example” as used hereinto describe various embodiments is intended to indicate that suchembodiments are possible examples, representations, and/or illustrationsof possible embodiments (and such term is not intended to connote thatsuch embodiments are necessarily extraordinary or superlative examples).

It is important to note that the construction and arrangement of thevarious exemplary embodiments are illustrative only. Although only a fewembodiments have been described in detail in this disclosure, thoseskilled in the art who review this disclosure will readily appreciatethat many modifications are possible (e.g., variations in sizes,dimensions, structures, shapes and proportions of the various elements,values of parameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter described herein. Forexample, elements shown as integrally formed may be constructed ofmultiple parts or elements, the position of elements may be reversed orotherwise varied, and the nature or number of discrete elements orpositions may be altered or varied. The order or sequence of any processor method steps may be varied or re-sequenced according to alternativeembodiments. Other substitutions, modifications, changes and omissionsmay also be made in the design, operating conditions and arrangement ofthe various exemplary embodiments without departing from the scope ofthe present invention.

1. An air filtration system comprising: a primary filter element; apre-cleaner positioned upstream of the primary filter element in an airflow direction; a bypass valve positioned upstream of the primary filterelement and downstream of the pre-cleaner in the air flow direction, thebypass valve actuatable between a first position and a second position,intake air to be filtered bypasses the pre-cleaner and flows to theprimary filter element when the bypass valve is in the first position,and intake air to be filtered is forced through the pre-cleaner prior toflowing to the primary filter element when the bypass valve is in thesecond position; an air quality characteristic sensor; and a controllerconfigured to: receive a feedback signal from the air qualitycharacteristic sensor indicative of a sensed air quality characteristicof the intake air, and actuate the bypass valve between the firstposition and the second position via an actuation mechanism.
 2. The airfiltration system of claim 1, wherein the bypass valve includes a flapand a hinge.
 3. The air filtration system of claim 1, wherein the bypassvalve includes a plurality of louvers.
 4. The air filtration system ofclaim 3, wherein each of the plurality of louvers includes a slat and acentral hinge.
 5. The air filtration system of claim 4, wherein each ofthe plurality of louvers move together between the first position andthe second position when actuated by the controller.
 6. The airfiltration system of claim 1, wherein the sensed air qualitycharacteristic relates to an amount of dust in the intake air, an amountof moisture in the intake air, or a combination thereof.
 7. The airfiltration system of claim 6, wherein the air quality sensor senses theair quality characteristic by counting and sizing particles passing byor through the air quality sensor.
 8. A filtration system comprising: afluid source providing a fluid to be filtered; a main filter; asecondary filter; a detector that detects a fill-up condition, astart-up condition, a change in fluid contaminant concentration, or afluid flow rate change of a system using the fluid; a valve that can beopened or closed so as to switch the filtration system between a normalfiltration mode and an enhanced filtration mode, the enhanced filtrationmode corresponding to an operating mode in which an increased amount ofthe fluid to be filtered is filtered through the secondary filterelement than when in the normal filtration mode; an electronic controlunit having a memory and a processor, the electronic control unitconfigured to: receive a feedback signal from the detector indicative ofa fill-up event, a start-up event, a change in fluid contaminantconcentration, or a fluid flow rate change, and switch between thenormal filtration mode and the enhanced filtration mode in response tothe fill-up event, the start-up event, the change in fluid contaminantconcentration, or the fluid flow rate change.
 9. The filtration systemof claim 8, wherein when the filtration system is in the normalfiltration mode, no fluid to be filtered flows through the secondaryfilter.
 10. The filtration system of claim 8, wherein when thefiltration system is in the normal filtration mode, some fluid to befiltered flows through the secondary filter.
 11. The filtration systemof claim 8, wherein the fluid source is a fluid tank, and wherein thesecondary filter is part of a fluid recirculating loop that routes fluidthat passes through the secondary filter back to the fluid tank.
 12. Thefiltration system of claim 11, wherein the detector senses at least oneof whether a fluid tank cap of the fluid tank is in place or has beenremoved, changes of a fluid level in the fluid tank, changes in a fluidflow rate of the fluid, contaminant concentration in the fluid, orwhether a system using the fluid has been turned on.
 13. The filtrationsystem of claim 8, wherein the system using the fluid is an internalcombustion engine.
 14. The filtration system of claim 8, wherein thesystem using the fluid is a hydraulic system.
 15. The filtration systemof claim 8, further comprising a pump that further induces fluid flowthrough the secondary filter.
 16. A method of switching a filtrationsystem between a normal filtration mode and an enhanced filtration modebased on a detected event, the method comprising: receiving, by anelectronic control unit of the filtration system, a feedback signal froma sensor of the filtration system; determining, by the electroniccontrol unit, that the feedback signal corresponds to a fill-up event ora start-up event; activating, by the electronic control unit, theenhanced filtration mode of the filtration system, the enhancedfiltration mode corresponding to an operating mode of the filtrationsystem in which an increased amount of the fluid to be filtered passesthrough a filtration component than when in the normal filtration mode.17. The method of claim 16, further comprising reverting, by theelectronic control unit, the filtration system back into the normalfiltration mode after a determined duration.
 18. The method of claim 17,wherein the duration represents a time period for which the filtrationsystem is in the enhanced filtration mode.
 19. The method of claim 17,wherein the duration represents an amount of time needed to filter anamount of fluid during the enhanced filtration mode.
 20. The method ofclaim 17, wherein the duration represents an amount of time needed toremove an amount of contaminant from the fluid during the enhancedfiltration mode.
 21. The method of claim 17, wherein the duration isbased at least in part on a period of time a fluid flow rate ischanging.
 22. The method of claim 17, wherein the additional filtrationcomponent is a kidney loop filter.
 23. The method of claim 17, whereinthe additional filtration component is a prefilter positioned upstreamof a main filter.
 24. A filtration system comprising: a fluid sourceproviding a fluid to be filtered; a main filter; a secondary filter; afluid quality characteristic sensor that senses a fluid qualitycharacteristic of the fluid; a valve that can be opened or closed so asto switch the filtration system between a normal filtration mode and anenhanced filtration mode, the enhanced filtration mode corresponding toan operating mode in which an increased amount of the fluid to befiltered is filtered through the secondary filter than when in thenormal filtration mode; an electronic control unit having a memory and aprocessor, the electronic control unit configured to: receive a feedbacksignal from the detector indicative of a change in the fluid qualitycharacteristic of the fluid, and switch between the normal filtrationmode and the enhanced filtration mode in response to the change in thefluid quality characteristic.
 25. The filtration system of claim 24,wherein when the filtration system is in the normal filtration mode, nofluid to be filtered flows through the secondary filter.
 26. Thefiltration system of claim 24, wherein when the filtration system is inthe normal filtration mode, some fluid to be filtered flows through thesecondary filter.
 27. The filtration system of claim 24, wherein thefluid source is a fluid tank, and wherein the secondary filter is partof a fluid recirculating loop that routes fluid that passes through thesecondary filter back to the fluid tank.
 28. The filtration system ofclaim 24, wherein the system using the fluid is an internal combustionengine.)
 29. The filtration system of claim 24, wherein the system usingthe fluid is a hydraulic system.
 30. The filtration system of claim 24,wherein the fluid quality characteristic is an amount of contaminant inthe fluid.
 31. A filtration system comprising: a fluid source providinga fluid to be filtered; a main filter; a secondary filter; a detectorthat detects a fill-up condition, a start-up condition, a change influid contaminant concentration, or a fluid flow rate change of a systemusing the fluid; a pump that routes the fluid to the secondary filtersuch that the pump can be activated and deactivated to switch thefiltration system between a normal filtration mode and an enhancedfiltration mode, the enhanced filtration mode corresponding to anoperating mode in which an increased amount of the fluid to be filteredis filtered through the secondary filter than when in the normalfiltration mode; an electronic control unit having a memory and aprocessor, the electronic control unit configured to: receive a feedbacksignal from the detector indicative of a fill-up event, a start-upevent, a change in fluid contaminant concentration, or a fluid flow ratechange, and switch between the normal filtration mode and the enhancedfiltration mode in response to the fill-up event, the start-up event,the change in fluid contaminant concentration, or the fluid flow ratechange by activating the pump.
 32. The filtration system of claim 31,wherein when the filtration system is in the normal filtration mode, nofluid to be filtered flows through the secondary filter.
 33. Thefiltration system of claim 31, wherein when the filtration system is inthe normal filtration mode, some fluid to be filtered flows through thesecondary filter.
 34. The filtration system of claim 31, wherein thefluid source is a fluid tank, and wherein the secondary filter is partof a fluid recirculating loop that routes fluid that passes through thesecondary filter back to the fluid tank.
 35. The filtration system ofclaim 34, wherein the detector senses at least one of whether a fluidtank cap of the fluid tank is in place or has been removed, changes of afluid level in the fluid tank, changes in a fluid flow rate of thefluid, contaminant concentration in the fluid, or whether a system usingthe fluid has been turned on.
 36. The filtration system of claim 31,wherein the system using the fluid is an internal combustion engine. 37.The filtration system of claim 31, wherein the system using the fluid isa hydraulic system.
 38. The filtration system of claim 31, furthercomprising a pump that further induces fluid flow through the secondaryfilter